Piston



Nov. 30, 1937. A NE 2,100,719

PISTON Filed Dec. 5, 1933 5 Sheets-Sheet l INVENTOR:'

'Kk; ATTORNEY Nov. 30, 1937. I A. 1.. NELSON 2,100,719

PISTON Filed Dec. 5, 1933 5 Sheets-Sheet 2 INVENTOR.

BY x :ORNEY Nov. 30, 1937. A. L. NELSON 2,100,719

PISTON Filed Dec. 5, 1933 5 Sheets-Sheet 3 INVENTOR Z iaogwz. nzwb MmeNov. 30, 1931 2,100,719

UNITED STATES PATENT OFFICE PISTON Adolph Nelson, Detroit, Mich.Application December 5, 1933, Serial No. 709,958 12 Claims. (01. 309-11)This invention provides an improved constructhe head by a slot, and thehead has an oiltion for pistons, especially for those formed of ringgroove located above the slot and oil holes light-weight materials suchas alloys of alumiextending through the wall of the head at the num.These alloys have many well-known adbottom of the groove, the oil holesbeing placed vantages in pistons for internal combustion enso as toavoid weakening of the head and to pro- 5 gines, but their chiefdisadvantage over castvide for better lubrication of the thrust faces.iron, formerly-"used exclusively, is their higher Additional objects andadvantages of the inrate of thermal expansion. The piston of the ventionwill become apparent as the description present invention has featuresof construction proceeds.

which combine to overcome this disadvantage. While a preferred form ofthe invention is dis- 10 An important feature of the invention residesclosed herein for purposes of illustration, it in the provision of apiston having uninterrupted should be understood that various changesmay arc-shaped parts under the pin bosses, and a be made withoutdeparture from the spirit of pair of openings or slots in the pistonskirt, each the invention as set forth and claimed.

of said openings being placed so as to have a In the drawings: 15

horizontal leg extending below a pin boss and a i Fig. 1 is a sideelevation of a piston embodyvertical leg extending between the pin bossand ing the invention.

a thrust face, thereby increasing the flexibility Fig. 2 is a partialsection on line 2-2 of Fig. 1. of a portion of the skirt. Fig. 31s asection on line 33 of Fig. 2.

On' the side of each pin boss opposite the open- Fig? 4 is a section online 4-4 of Fig. 3. 20

ings there is provided a web which connects the Fig. 5 is a section online 5-5 of Fig. 1. pin boss to one of the thrust faces, and a rib Fig.6 is a section on line 6-6 of Fig. 2. extends at a downward angle fromthe pin boss Fig. 7 is a section on line 1-1 of Fig. 3. along the web,the purpose ofthis rib being to Figs. 8 and 9 are diagrammatic viewsillustratintroduce a beneficial distortion into the lower ing the action.of the lower cylindrical ring of 25 part of the skirt. the piston.

The thrust face on the side opposite the open- The. piston disclosed inthe drawings includes ings is separated from th head by a, slot, andahead In having atop wall and acylindrical side a slot extendsdownwardly into this thrust face Wall. a Skirt h Skirt including ChordalW to a point below the upper ends of the openings. l2, a lower annularpart I 3, and thrust faces I4 30 The amount of overlap of this downwardslot and I5. Piston pin bosses I6 are carried by with the openingsdetermines the flexibility of chordal webs l2. the skirt to a largedegree. When the piston is operating in an engine the The skirt isfinished in such a way as to give entire force applied to the top of thepiston is it an oval external shape throughout its length, transmittedto the connecting rod through the 35 the small diameter coinciding withthe axis of parts of the piston connecting the pin bosses the piston pinbosses. The expansion of the pisto the head. A feature of the presentinvention ton head under operating temperatures acts lies in an improvedrib section between the head through the slanting ribs to help round outI and each pin boss. These sections should have 40 the oval shapethereby preventingundue increase minimum weight with maximum strengthagainst 40 in skirt size on the diameter perpendicular to breakage,especially against strains tending to the axis of the pin bosses. bendthe pin bosses inwardly with relation to The upper part of the skirt isprotected from the head. So'far as these strains are concerned theeffects of undueexpansion by curved reliefs the neutral axis of thesection may be taken as in connection with the downward slot and the theline illustrated in Figure 4, which is at right 45 oval shape of theskirt, while the lower portion of .angles to axis of the piston pinbosses. In order the skirt is protected by the openings and the to givemaximum strength the parts are arranged action of the slanting ribs onthe oval skirt. 7 so that large masses of metal are disposed on Theinvention also includes an improved rib each side of and spaced aconsiderable distance section connecting each pin boss and the head fromthe neutral axis of the section. In the 50 so as to provide maximumstrength -.against embodiment illustrated this object is attained bystrains placed upon this section during opera-- the followingcombination of parts: tion of the engine. A tapered web member II hasits wide end A further object is to provide a piston in which. connectedto the side wall of the head and its at least one of the thrust faces isseparated from lower end attached to the outer end of the pin 55 bosses,and is located outwardly of the neutral axis of the rib section andacross the axis of the piston pin bosses. The parts of the chordal websl2 that extend between the head and pin boss are located inwardlyfromthe neutral axis of the section. A central reinforcing rib l8extends upwardly along the inner wall of web I! from the boss to thehead, continues across the under wall of the head and then extendsdownwardly along the web H on the opposite side of the piston. Twotransverse inclined side ribs l9 extend from the pin boss along the sidewall of the head to the top wall, these ribs projecting inwardly fromthe lateral sides of the tapered web I! and after connecting with theweb l2 extend still farther inwardly in order to give an added amount ofmetal spaced inwardly from the neutral axis of the section. Thisarrangement is substantially a U beam with the legs of the U crossingthe neutral axis of the section and with the additional reinforcing rib18 disposed vertically in the channel of the U, a construction whichprovides substantially large masses of metal disposed on opposite sidesof, and spaced from, the neutral axis of the section and offeringmaximum resistance to compressive and tensional stresses resulting fromforces which tend to twist the section about the neutral axis.

The upper end of the thrust face I4 is separated from the head by a slot20, and a slot 2| extends part way downward in thrust face I4. Thrustface I5 is unslotted and remains attached to the head. Each thrust facehas its lateral edges relieved along curved lines which converge towardthe top of the thrust face.

Each of the chordal webs i2 is formed with an opening or slot 23,usually in the process of casting. Each of the openings has itshorizontal leg extending from the side of thrust face l5 between theupper edge of the annular part [3 and the pin boss, while its verticalleg extends upwardly between the pin boss and the thrust face l5. Thesevertical legs extend upwardly past the lower end of slot 2|, and theamount of overlap of this downward slot 2| with the vertical legs of theL openings determines to a large extent the relative flexibility of theskirt. In the structure illustrated herein this overlap is equal to 40per cent of the diameter of the skirt, but this overlap can be varied asdesired. It is clearly shown in Fig. 1 that the opening 23 extendsacross a vertical axis passing through the center line of'the pin bossesand extends farther toward-the thrust face and is wider on the side ofsaid vertical axis toward the thrust face i5 than toward thrust face l4.

A tapered rib 22 extends downwardly from each pin boss at an anglebetween the vertical and the horizontal. Each of these ribs extendsalong the outer surface of one of the chordal webs I2 and is directedtoward the slotted thrust face ll. One purpose of the ribs 22 is toreinforce the webs l2 against possible cracking and another purpose is"to introduce a beneficial distortion into the piston skirt in a mannerthat will now be described.

Where the head of a piston is separated from the skirt by a slot orslots, the head, as it expands under the heat of operation, spreads the.piston pin bosses, and if there is a rigid connection extendingstraight downwardly from the bosses to the lower annular part, thelatter part is pulled outwardly under the bosses, this distortion of theskirt decreasing the diameter of the skirt on the diameter at rightangles to the axis of the pin bosses.

Thus in Fig. 8, B represents points on the lower ring under the pinbosses. If the expansion of the pin bosses is transmitted directly tothe points B, the skirt wall at these points will be carried outwardly adistance G, and the diameter at right angles to the axis of the bosseswill be correspondingly diminished by the amount D.

However, in the piston illustrated herein, the outward movement of thebosses is not transmitted to the points B but is carried by the ribs 22to the points A, as shown in Fig. 9, thereby deflecting the skirt atthese points by the distance G. This action produces a skirt deflectionF on the axis of the pin bosses, which is greater than the distance G,and causes a corresponding defiection E on the diameter at right anglesto the axis of the bosses; distance E being greater than distance D ofFig. 8.

In both cases the lower part I3 is ground oval with the short axis ofthe oval corresponding with the axis of the bosses so as to permitoutward movement of the wall along this axis. The use, of the ribs 22transmits the outward movement of the bosses to the lower annular partat points spaced away from the axis of the bosses, both points beinglocated on the same side of said axis, thereby utilizing greaterleverage and causing a much greater decrease in the effective diameterof the skirt than if there. were a vertical connection from the bossesto the lower circular part. This beneficial distortion produces arelatively large decreasein the effective diameter of the skirt byforces within the piston and without depending on pressure of thecylinder wall against the skirt.

In grinding the skirt it is given an oval shape throughout its entirelength, the small diameter of the oval coinciding with the axis of thepiston .pin bosses. It is desirable to use as little oval as possible atthe thrust faces because the less oval used, the better the bearing onthe thrust faces. More oval is permitted under the pin bosses to obtainproper control of the diameter perpendicular to the pin bosses in themanner above described.

Parts of the lower part I3 form uninterrupted arcs under the pin bosses,and these arcs cooperate with the openings 23 in the beneficialdistortion above described.

In the above-described skirt construction the excessive expansion of thelight-weight alloy is taken care of atthe bottom of the skirt by theopenings 23 and the beneficial distortion, and at the top of the skirtby the T slot, the curved reliefs and the beneficial distortion. Thesecombinations overlap to take care of the expansion of the middle portionof the skirt.

The piston head is provided with ring grooves 24 for compression ringsand with a ring groove 25 for an oil control ring. Oil holes 26 areprovided to permit escape of oil to the interior of the piston and aparticular feature of this invention lies in the disposition of theseoil holes.

In the usual construction, 8 to 12 oil holes are spaced equally aboutthe circumference of the piston head, and where one or both of thethrust faces are slotted from the head, the presence of the oil holesclose to the center line passing through the thrust faces (P--P in Fig.7) causes a weakening of the piston head above the slot. The presentinvention avoids this weakening by spacing the oil holes unequally aboutthe head, the two holes nearest to the center line PP on the side of theslot 20 being spaced farther apart than the rest of the holes. .In theembodiment illustrated these holes are spaced about away from the centerline. This wider spacing of the oil holes can be used above one or boththrust faces. Tests have shown that this arrangement of oil holes'issubstantially as eifective as holes equally spaced asfar as oil economyis concerned and1the'arrangement disclosed herein gives substantialincrease in the strengthof the head.

Thus, for example, with a certain piston having a thrust face slottedfrom the head and with oil holes equally spaced about the head, the headcracks on application of about 8500 lbs. across Another advantage ofthis placing ofthe oil holes is that more oil is left on the cylinderwall in the path of the thrust face This is due to the face that theoilis not drained from the oil-ring I wardly from the side wall of thehead to the 'groove so, rapidly above the thrust face and the grooveretains more oil at this place. In this way the thrust faces, whichcarry the chief bearing loads against the cylinder wall, are givenbetter lubrication without reducing the eificiency of the oil ring atthe sides of the bore that do not take the thrust loads.

. I claim:

1. A piston comprising a head, pin bosses connected to the head, a skirthaving a lower annular part and oppositely arranged thrust faces, one ofthe thrust faces being separated from the'head by a slot and having aslot extending downwardly from the top of the thrust face, chordal websextending between the slotted face and the pin bosses said webs beinghomogeneous with the slotted face and the pin bosses and a tapered ribextending from each pin boss along the outside of each of said webs at adownward,

angle between the vertical and the horizontal,

- and toward the slotted thrust face.

2. A piston comprising a head, pin bosses conton pin boss connected toeach web, a tapered rib extending jfrom each pin boss along a web at adownward angle between the vertical and horizontal, and each web beingformed with an L- shaped opening disposed with its horizontal legextending below a pin boss and with its vertical leg extending, upwardlyalong the pin boss on the side opposite the tapered rib.

3. A pistonlcomprising a head, a skirt having a lower annular part andoppositely arranged thrust faces, lone of the thrust faces having itsupper end separated from the head by a slot and having a slot extendingdownwardly from the top of the thrust face, a pair of chordal webs extending between the thrust faces and homogeneous therewith, a piston pinboss connected to each web, each web being formed with an L- shapedopening disposed with its horizontal leg extending between a pin bossand the lower annular part of the skirt and with its vertical legextending between the pin boss and the unslotted thrust face and atapered rib extending from each pin boss along a web at a downward anglebetween the vertical and the horizontal, and to ward the slotted thrustface.

4. A piston comprising a head having a top and a cylindrical side wall,a skirt, and piston pin bosses connected to the head, a horizontalsection taken transversely of the parts connecting the-pin bosses to thehead showing that said parts include a chordal web extending downwardlyfrom the-sidewall of the head to the outer endof the pin boss, a pair ofinner chordal webs extending from the inner part of the pin boss to the"side wall of the head and connected to the skirt, the inner and outerwebs lying in different vertical planes, and a pair of transverseribshaving their lower ends connected to the inner end of the pin bossand extending alon said side wall and joining the top of the head andconnecting the sides of the outer web with the inner webs.

5. A piston comprising a head having a top and a cylindrical side wall,a skirt, and piston pin bosses connected to the head, a horizontalsection taken transversely of the parts connecting the pin bosses to thehead showing that said partsinclude a chordal web extending downouterend of the pin boss, a pair of inner chordal webs extending from theinner part of the pin boss to the side wall of the head and connectedtothe skirt, the inner and outer webs lying in different verticalplanes, and a pair of transverse ribs having their lower ends connectedto the inner end of the pin boss and extending along said side wall andjoining the top of the head and connecting the sides of the outer webwith the inner webs, said transverse ribs diverging from each other asthey approach the top of the head.-

6. A piston comprising a head having a top and a cylindrical side wall,a skirt, and piston pin bosses connected to the head, a horizontalsection'taken transversely of the parts connecting the pin bosses to thehead showing that said parts include a chordal web extending downwardlyfrom the side wall of the head to the outer .end:of the pin boss, a pairof inner chordal webs extending from the inner part of the pinboss tothe side wall of the head and connected to the skirt, the inner andouter webs lying in different vertical planes, and a pair of transverseribs having their lower ends connected to the inner end of the pin bossand extending along said side -wall and joining the top of the head andconnecting the sides of the outer web with the inner webs, and a centralrib extending from the pin boss to the top of the head and connected tothe outer web.

'7. An all-aluminum piston comprising a head, a skirt having a lowerannular part and oppositely arranged thrust faces, a pair of chordalwebs extending between the thrust faces and homogeneous therewith, apiston pin boss located on each web, a tapered rib extending from thelower part of each pin boss along a chordal web toward one of the thrustfaces, each web being 8. A piston comprising a head, a skirt having alower annular part and oppositely arranged thrust faces, one of thethrust faces being formed with a vertically extending slot, a pair ofchordal webs extending between the thrust faces and homogeneoustherewith, a piston pin boss located on each web, a tapered ribextending from the lower part of each pin boss along a. chordal webtoward one of the thrust faces, said tapered ribs being homogeneous withthe webs and extending toward the slotted thrust face, each web beingformed with an opening extending below the pin boss, the openingextending across a vertical plane passing through the center line of thepin bosses, each opening extending a shorter distance toward the thrustface and being narrower on the side of said axis toward the'slottedthrust face than toward the other thrust face, the outer surface of theskirt having an oval shape with the minor axis of the oval coincidingwith the axis of the piston pin bosses.

9. A light-metal trunk piston having a head and a skirt, wrist-pinbearings, a frame structure connecting said bearings with said head, aflat web extending transversely of the wrist pin axis and connectingsaid skirt with said structure, said skirt having a circumferentiallycomplete rim separated from said web by a horizontally extending openingand being split longitudinally at one of its bearing faces, and atapered rib extending from the lower part of each pin boss to the web,said rib being homogeneous with the boss and with the web and extendingtoward the split thrust face.

10. A light-metal trunk piston having a head and a skirt, wrist-pinbearings, a frame structure connecting said bearings with said head, aflat web extending transversely of the wrist-pin axis and connectingsaid skirt with said structure, said skirt being split longitudinally atone of its bearing faces and having a circumferentially complete lowerrim separated from said web by a horizontally extending aperture belowthe wrist-pin bearing, said rim being thickened below said aperture tostiffen the same, and a tapered rib extending from the lower part ofeach pin boss to the web, said rib being homogeneous with the boss andwith the web and extending toward the split thrust face.

11. An all-aluminum piston comprising a head,

-a skirt having a lower annular part and oppositely arranged thrustfaces, a pair of chordal webs extending between the thrust faces andhomogeneous therewith, a piston pin boss located on each Web, a taperedrib extending from the lower part of each pin boss'along a chordal webtoward one of the thrust.faces,,each web being formed with an opening.extending below the pin boss, the opening extending across a verticalaxis passing through the center line of the pin bosses, each openingextending farther toward the thrust face and being wider on the side ofsaid axis away from the tapered rib.

12. A piston comprising a head, a skirt having a lower annular part andoppositely arranged thrust faces, one of the thrust faces being formedwith a vertically extending slot, a pair of chordalwebs extendingbetween the thrust faces and homogeneous therewith, a piston pin bosslocatedv on each web, a tapered rib extending from 'the lower part ofeach pin boss along a chordal web toward one of the thrust faces, saidtapered ribs being homogeneous with the webs and extending toward theslotted thrust face, each web being formed with an opening extendingbelow the pinboss, the opening extending across a vertical axis passingthrough the center line of the pin bosses, each opening extending ashorter distance toward the thrust face and being narrower on the sideof said axis toward the slotted thrust face than toward the other thrustface.

ADOLPH L. NELSON.

D l s c L A'l M 1-: R 2,100,719.Adolph L. Nelson, Detroit, Mich.PIs'roN. Patent dated November 30, 1937. Aluminum ct: Brass Corporation.

Disclaimer filed December 29, 1939, by the assignee, Bohn Hereby entersthis disclaimer to claims 4 to 12 inclusive of said patent.

[Oflic'ial Gazette January 30, 1940.]

8. A piston comprising a head, a skirt having a lower annular part andoppositely arranged thrust faces, one of the thrust faces being formedwith a vertically extending slot, a pair of chordal webs extendingbetween the thrust faces and homogeneous therewith, a piston pin bosslocated on each web, a tapered rib extending from the lower part of eachpin boss along a. chordal web toward one of the thrust faces, saidtapered ribs being homogeneous with the webs and extending toward theslotted thrust face, each web being formed with an opening extendingbelow the pin boss, the opening extending across a vertical planepassing through the center line of the pin bosses, each openingextending a shorter distance toward the thrust face and being narroweron the side of said axis toward the'slotted thrust face than toward theother thrust face, the outer surface of the skirt having an oval shapewith the minor axis of the oval coinciding with the axis of the pistonpin bosses.

9. A light-metal trunk piston having a head and a skirt, wrist-pinbearings, a frame structure connecting said bearings with said head, aflat web extending transversely of the wrist pin axis and connectingsaid skirt with said structure, said skirt having a circumferentiallycomplete rim separated from said web by a horizontally extending openingand being split longitudinally at one of its bearing faces, and atapered rib extending from the lower part of each pin boss to the web,said rib being homogeneous with the boss and with the web and extendingtoward the split thrust face.

10. A light-metal trunk piston having a head and a skirt, wrist-pinbearings, a frame structure connecting said bearings with said head, aflat web extending transversely of the wrist-pin axis and connectingsaid skirt with said structure, said skirt being split longitudinally atone of its bearing faces and having a circumferentially complete lowerrim separated from said web by a horizontally extending aperture belowthe wrist-pin bearing, said rim being thickened below said aperture tostiffen the same, and a tapered rib extending from the lower part ofeach pin boss to the web, said rib being homogeneous with the boss andwith the web and extending toward the split thrust face.

11. An all-aluminum piston comprising a head,

-a skirt having a lower annular part and oppositely arranged thrustfaces, a pair of chordal webs extending between the thrust faces andhomogeneous therewith, a piston pin boss located on each Web, a taperedrib extending from the lower part of each pin boss'along a chordal webtoward one of the thrust.faces,,each web being formed with an opening.extending below the pin boss, the opening extending across a verticalaxis passing through the center line of the pin bosses, each openingextending farther toward the thrust face and being wider on the side ofsaid axis away from the tapered rib.

12. A piston comprising a head, a skirt having a lower annular part andoppositely arranged thrust faces, one of the thrust faces being formedwith a vertically extending slot, a pair of chordalwebs extendingbetween the thrust faces and homogeneous therewith, a piston pin bosslocatedv on each web, a tapered rib extending from 'the lower part ofeach pin boss along a chordal web toward one of the thrust faces, saidtapered ribs being homogeneous with the webs and extending toward theslotted thrust face, each web being formed with an opening extendingbelow the pinboss, the opening extending across a vertical axis passingthrough the center line of the pin bosses, each opening extending ashorter distance toward the thrust face and being narrower on the sideof said axis toward the slotted thrust face than toward the other thrustface.

ADOLPH L. NELSON.

D l s c L A'l M 1-: R 2,100,719.Adolph L. Nelson, Detroit, Mich.PIs'roN. Patent dated November 30, 1937. Aluminum ct: Brass Corporation.

Disclaimer filed December 29, 1939, by the assignee, Bohn Hereby entersthis disclaimer to claims 4 to 12 inclusive of said patent.

[Oflic'ial Gazette January 30, 1940.]

